Hydrogen fluoride is used in the manufacture of Freons (which destroy ozone in the stratosphere and in the production of aluminum metal. It is prepared by the reaction:
CaF2 + H2SO4 --> CaSO4 + 2HF
In one process, 5.85 kg of CaF2 is treated with an excess of H2SO4 and yields 2.85 kg of HF. Calculate the percent yield of HF.